Families of Volatile Metal for Use in ALD Applications
Strem Chemicals Inc in the US works with Roy Gordon’s Group at Harvard University, who produce transition metal amidinates for metal, nitride and oxide layer deposition allowing us Strem Chemicals UK to distribute them in the UK and Ireland
Atomic Layer Deposition (ALD) is a vapour phase technique capable of producing thin films of a variety of materials. As device requirements push toward smaller and more spatially demanding structures, ALD has demonstrated potential advantages over alternative deposition methods. ALD offers exceptional conformity on high-aspect ratio structures, thickness control at the angstrom level, and tunable film composition from metal oxides to noble metals. ALD has emerged as a powerful tool for many industrial and research applications including ferroelectric memories, switches, radiation detectors, thin-film capacitors and microelectromechanical structures (MEMS). They also are affording significant improvements in solar cell devices, high-k transistors, solid oxide fuels, protective coatings, fuel cells, + ion- batteries and nanogratings.
ALD procedures feature alternating exposures of chemical precursors to form desired materials, often at significantly lower temperatures then CVD analogues allow. Typically, ALD processes are conducted at modest temperatures (<350 °C). While the selection of available precursors is impressive, it is not yet possible to grow every material by ALD. The selection is limited, in general, by the availability of reactants that can facilitate the process. The reactants should be volatile enough to enter the gas phase, while not decomposing until they react with the sample surface. The choice of reactants has economic implications, as the synthesis can be time consuming and the starting materials expensive. Unfortunately, there are no perfect set of reagents for all applications, so the choice of reagents involves trade-offs between cost, availability, safety, volatility and reactivity.
In this regard, amidinates of transition metals have recently arrived on the scene and have proven to be promising reagents for the future. These products have thermal stability and are reactive. The benefit of thermal volatility combined with opportunities to develop customized systems for low-temperature deposition, make these attractive precursors. In addition, their use leads to the elimination of corrosive halogens, and the amidinates are soluble in inert solvents at room temperature. Furthermore, these compounds are becoming more readily available.
The range of Roy Gordan amidinate compounds to include cobalt, copper, and iron analogues. Bus(N,N’-di-i-propylacetamidinato) cobalt (II), min. 98% CAS 635680-58-9 Bis(N,N’-di-sec-butylacetamidinato)dicopper(I),99% CAS 695188-31-9 and Bis(N,N’-di-t-butylacetamidinato)iron (II), min. 98% CAS 635680-56-7 is an effective precursor (with metal nitrogen bonds) used in the Atomic Layer Deposition of metals, nitrides, and oxides.
The product sublimes at 50°C (50 mTorr) and has a melting point of 84°C. Cobalt oxide (CoO) films have been grown on Si(001) by (ALD) at low temperatures (170–180 °C), using water as a co-reactant with 27-0485 CAS 635680-58-9 Highly conformal CoSi2 films, with low resistivity, are formed using 27-0485 via an annealing of ALD Co thin films, in addition to CoSi2 nanowires. CAS 695188-31-9 has a vapour pressure of 0.1mm at 85°C and serves as a good precursor (with metal nitrogen bonds)for use in Atomic Layer Deposition of metals, metal nitrides, and oxides CAS 635680-56-7 melts at 107°C and is very useful as an iron amidinate precursor in the deposition of iron, iron carbides and iron nitride thin films along with CAS 635680-56-7 which is one our latest additions in a Swavelok cylinder